1ZMQ_TCP(7) 0MQ Manual ZMQ_TCP(7)
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6 zmq_tcp - 0MQ unicast transport using TCP
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9 TCP is an ubiquitous, reliable, unicast transport. When connecting
10 distributed applications over a network with 0MQ, using the TCP
11 transport will likely be your first choice.
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14 A 0MQ endpoint is a string consisting of a transport:// followed by an
15 address. The transport specifies the underlying protocol to use. The
16 address specifies the transport-specific address to connect to.
17 For the TCP transport, the transport is tcp, and the meaning of the
19 address part is defined below.
20 Assigning a local address to a socket
22 When assigning a local address to a socket using zmq_bind() with the
23 tcp transport, the endpoint shall be interpreted as an interface
24 followed by a colon and the TCP port number to use.
25 An interface may be specified by either of the following:
27 • The wild-card *, meaning all available interfaces.
29 • The primary IPv4 or IPv6 address assigned to the interface, in its
31 numeric representation.
32 • The non-portable interface name as defined by the operating system.
34 The TCP port number may be specified by:
36 • A numeric value, usually above 1024 on POSIX systems.
38 • The wild-card *, meaning a system-assigned ephemeral port.
40 When using ephemeral ports, the caller should retrieve the actual
42 assigned port using the ZMQ_LAST_ENDPOINT socket option. See
43 zmq_getsockopt(3) for details.
44 Unbinding wild-card address from a socket
46 When wild-card * endpoint was used in zmq_bind(), the caller should use
47 real endpoint obtained from the ZMQ_LAST_ENDPOINT socket option to
48 unbind this endpoint from a socket using zmq_unbind().
49 Connecting a socket
51 When connecting a socket to a peer address using zmq_connect() with the
52 tcp transport, the endpoint shall be interpreted as a peer address
53 followed by a colon and the TCP port number to use. You can optionally
54 specify a source_endpoint which will be used as the source address for
55 your connection; tcp://source_endpoint;'endpoint', see the interface
56 description above for details.
57 A peer address may be specified by either of the following:
59 • The DNS name of the peer.
61 • The IPv4 or IPv6 address of the peer, in its numeric
63 representation.
64 Note: A description of the ZeroMQ Message Transport Protocol (ZMTP)
66 which is used by the TCP transport can be found at
67 http://rfc.zeromq.org/spec:15
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70 For the TCP transport, the high water mark (HWM) mechanism works in
71 conjunction with the TCP socket buffers handled at OS level. Depending
72 on the OS and several other factors the size of such TCP buffers will
73 be different. Moreover TCP buffers provided by the OS will accomodate a
74 varying number of messages depending on the size of messages (unlike
75 ZMQ HWM settings the TCP socket buffers are measured in bytes and not
76 messages).
77 This may result in apparently inexplicable behaviors: e.g., you may
79 expect that setting ZMQ_SNDHWM to 100 on a socket using TCP transport
80 will have the effect of blocking the transmission of the 101-th message
81 if the receiver is slow. This is very unlikely when using TCP transport
82 since OS TCP buffers will typically provide enough buffering to allow
83 you sending much more than 100 messages.
84 Of course if the receiver is slow, transmitting on a TCP ZMQ socket
86 will eventually trigger the "mute state" of the socket; simply don’t
87 rely on the exact HWM value.
88 Obviously the same considerations apply for the receive HWM (see
90 ZMQ_RCVHWM).
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93 Assigning a local address to a socket.
94 // TCP port 5555 on all available interfaces
96 rc = zmq_bind(socket, "tcp://*:5555");
97 assert (rc == 0);
98 // TCP port 5555 on the local loop-back interface on all platforms
99 rc = zmq_bind(socket, "tcp://127.0.0.1:5555");
100 assert (rc == 0);
101 // TCP port 5555 on the first Ethernet network interface on Linux
102 rc = zmq_bind(socket, "tcp://eth0:5555");
103 assert (rc == 0);
104 Connecting a socket.
106 // Connecting using an IP address
108 rc = zmq_connect(socket, "tcp://192.168.1.1:5555");
109 assert (rc == 0);
110 // Connecting using a DNS name
111 rc = zmq_connect(socket, "tcp://server1:5555");
112 assert (rc == 0);
113 // Connecting using a DNS name and bind to eth1
114 rc = zmq_connect(socket, "tcp://eth1:0;server1:5555");
115 assert (rc == 0);
116 // Connecting using a IP address and bind to an IP address
117 rc = zmq_connect(socket, "tcp://192.168.1.17:5555;192.168.1.1:5555");
118 assert (rc == 0);
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122 zmq_bind(3) zmq_connect(3) zmq_pgm(7) zmq_ipc(7) zmq_inproc(7)
123 zmq_vmci(7) zmq(7)
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126 This page was written by the 0MQ community. To make a change please
127 read the 0MQ Contribution Policy at
128 http://www.zeromq.org/docs:contributing.
1290MQ 4.3.4 01/21/2023 ZMQ_TCP(7)